In bringing thermostat control into the latest phase of its development, previous designs employing bimetal plates flexing due to temperature variation to actuate on/off switches have become undesirable means of regulating temperature. Accordingly, this patent describes a relatively inexpensive, purely electronic sensing and control thermostat capable of mode control and multiple (at least two) actuator control outputs, including the possibility of more than simple on/off control. Several features of the thermostat, including extending the range of application of the device, reducing power losses and internal device heating, and protecting the electronics are described herein.
Prior U.S. Pat. No. 4,776,514, shows a thermostat for electric baseboard heating without a fan coil control of a type which would ordinarily be installed, for example, in a domestic house. That thermostat has two terminals--one of which is connected to one side of the line voltage, and the other connected to a heater load, which is then connected to the other side of the line voltage. The thermostat itself contains a switch which must control large amounts of power in addition to some the of circuitry which enables the thermostat itself to be energized from the same line voltage source.